The presence of nonzero helicity in intergalactic magnetic fields (IGMF) has been suggested as a clear signature for their primordial origin. We extend a previous analysis of diffuse Fermi-LAT gamma-ray data from 2.5 to more than 11 years and show that a hint for helical magnetic fields in the 2.5 year data was a statistical fluctuation. Then we examine the detection prospects of helical magnetic fields using individual sources as, e.g., TeV gamma-ray blazars. We find that a detection is challenging employing realistic models for the cascade evolution, the IGMF and the detector resolution in our simulations.

• Received 21 August 2020
• Accepted 15 September 2020

DOI:https://doi.org/10.1103/PhysRevD.102.083001